Most of the information relating to the nutritional quality of proteins in food systems may not be relevant to contemporary food systems. Modern processing techniques are, in many instances, drastically different from those employed 15 to 20 years ago. Thus, the principal objective of this proposal involves a reevaluation of the effects of contemporary processes on the nutritive quality of food proteins. Protein quality will be estimated by in vitro sequential digestion with a pepsin-pancreatic enzyme system followed by analysis for liberated essential amino acids. Essential Amino Acid Indices will be compared with Protein Efficiency Ratios (PER) derived from animal (rats) assays. Cow's milk will be employed as a typical food system subjected to contemporary processing procedures. Model systems composed of various protein types (whole casein, alpha s-casein, beta-casein, kappa-casein and beta-lactoglobulin) representing non-structured proteins (little, if any alpha-helix), glycoproteins, globular proteins, SH and -S-S- bearing proteins will be subjected to various treatments (heat, pressure, freezing, dehydration and acidulation) both in the presence and absence of reducing sugars, various salt systems, specific ions, fatty acids, etc. These protein systems will be assessed for nutritive quality which will be correlated with induced changes in molecular parameters. These studies should provide essential information relative to the effects of specific processes and protein types on the nutritive quality of food proteins.